Ketamine (K)

Short term: Ketamine is an anaesthetic that makes people feel relaxed and high, but its effects are unpredictable.

You may not be aware of what you are doing after taking it so you risk, for example, having an accident.

Long term: The longer term effects may include flashbacks, losing your memory and not being able to concentrate.

Regular use can cause depression and, occasionally, psychotic symptoms such as hallucinations.

Ketamine can also make existing mental health problems worse.

Solvents (gases, glues and aerosols)

Short term: Solvents make you feel high and disorientated. They can cause aggression, mood swings and hallucinations.

Long term: Heavy use of solvents can damage your brain, particularly the bit that controls your movements.

Speed and crystal meth (amphetamine and methamphetamine)

Short term: Speed can make you feel energetic and confident but it can also cause anxiety, paranoia and aggression.

The "comedown" can make you feel lethargic and down, and you may have problems with concentrating and learning.

The effects of crystal meth are similar to speed but more exaggerated and longer-lasting. The comedown can be worse too.

Long term: Heavy use of speed can lead to anxiety, depression, irritability, aggression and paranoia. It can also cause psychotic symptoms, such as hallucinations.

Regular use of crystal meth can lead to brain damage, but this can be reversed if you don't use the drug for a long time.

Tranquillisers (benzodiazepines)

Short term: Tranquillisers, such as diazepam, are sedative drugs. They are used to treat anxiety and aid sleep.

Big doses of tranquillisers can affect your memory and make you drowsy.

Long term: Your body quickly gets used to benzodiazepines and soon needs more to get the same effect. You can get addicted in just a few weeks. Withdrawal can be difficult and make you feel panicky, anxious and depressed.

Sudden withdrawal from high doses can be very dangerous and cause seizures (fits).